1. Field of the Invention
The invention relates to methods for making a field emission cathode and, particularly, to a laser-based method for making a carbon nanotube-based field emission cathode.
2. Discussion of Related Art
Carbon nanotubes are a novel carbonaceous material discovered and reported in an article by Sumio Iijima, entitled “Helical Microtubules of Graphitic Carbon” (Nature, Vol. 354, Nov. 7, 1991, pp. 56-58). Carbon nanotubes can transmit an extreme high electrical current and emit electrons at a very low voltage of less than 100 volts, which make it a very promising potential material for field emission applications.
Generally, the carbon nanotubes used for field emission are produced by arc discharge method or chemical vapor deposition method. The method for applying carbon nanotubes in field emission includes the steps of: printing a patterned layer of conductive grease on a conductive base with a predetermined quantity of carbon nanotubes dispersed therein and treating the layer of grease by peeling parts of the grease to expose ends of the carbon nanotubes to emit electrons. However, the step of peeling quite often destroys the carbon nanotubes. Moreover, the carbon nanotubes for emitting electrons generally lie on the conductive base. Thus, the field emission efficiency thereof is relatively low, and the stability thereof is less than desired.
What is needed, therefore, is to provide a laser-based method for making a carbon nanotube-based field emission cathode in which the above problems are eliminated or at least alleviated.